Various types of chucks and mandrels are utilized for supporting workpieces to permit machining and finishing operation to be carried out thereon. Such chucks and mandrels, herein referred to as workholders for convenience in description, are typically designed to create a specific supporting or gripping cooperation with a workpiece and, as such, several different workholders must often be provided in order to permit a wide variety of machining or finishing operations to be carried out. If such operations are to be carried out on a single machine tool, then the changing from one workholder to another is typically a rather complex and time consuming operation. In addition, a typical workholder is normally suitable solely for a very limited size range of workpiece, and the changing or modifying of the workpiece to accommodate a different size of workpiece is generally a complex and time consuming operation.
There is known a collet-type chuck which employs a collet employing a plurality of rubberlike segments joined to intermediate plates so as to define a collet sleeve, the sleeve having an outer conical surface which is acted on by a stationary wedging surface to effect compression of the collet sleeve into engagement with a workpiece. In this known arrangement, the forward end of the collet sleeve is acted on by an axially movable cap, the latter being axially displaced in response to rotation of an external nut. Hence, with this arrangement, both the actuating cap (which defines the front face of the chuck) and the collet sleeve are moved axially inwardly during actuation, and hence this draws the workpiece inwardly and prevents accurate axial positioning of the workpiece.
Accordingly, it is an object of this invention to provide an improved workholder arrangement which employs a support module which can have one of several different workpiece engaging units readily and interchangeably mounted thereon so that the same workholder module can be readily adapted to function several different ways, such as a collet chuck, a step chuck and an expanding mandrel. The improved workholder arrangement of this invention hence greatly simplifies the interchanging of the primary function of the workholder, and at the same time facilitates the interchanging of the workholder to accommodate different size ranges.
A further object is to provide an improved workholder arrangement, as aforesaid, which can be adapted to form a collet-type chuck employing a deformable collet sleeve constructed of an elastomeric material to enable gripping of workpieces having a wide range of sizes and properties, and the gripping of workpieces over only a short axial extent thereof. An improved workholder employing this elastomeric collet sleeve cooperates with an axially-movable actuator, such as a draw or push bar, to permit actuation of the elastomeric collet sleeve without causing axial movement thereof so as to permit accurate axial positioning of the workpiece during gripping thereof.
A still further object of the invention is to provide an improved workholder arrangement, as aforesaid, which employs a support module having a housing which attaches to the basic machine tool and slidably supports therein an activating sleeve defining an interior conical surface thereon, the activating sleeve being adapted for direct connection to and being axially movable by a draw or push bar. To create a collet chuck, an elastomeric sleeve is positioned within the conical bore of the activating sleeve and is restrained therein by an end cap which is threadably secured to the front end of the housing so that, upon forward axial displacement of the activating sleeve, the elastomeric collet sleeve is radially compressed inwardly for gripping the workpiece, the elastomeric collet sleeve being axially restrained by its engagement with the removable end cap. To convert to an expanding mandrel, the end cap and collet sleeve are removed, and a slidable actuator is positioned within the housing so as to abut against the forward end of the activating sleeve. The actuator has a forwardly projecting conical wedge which is received within a conical bore formed in a split cylindrical mandrel, the latter having an integral mounting plate which is threaded onto the front end of the housing. Axial displacement of the activating sleeve by the push bar, and corresponding axial displacement of the actuator causes resilient radial expansion of the mandrel for gripping a workpiece. To convert the workpiece arrangement to a step-type chuck, the mandrel and actuator are removed from the support module, following which an end cover or closer is threaded onto the forward end of the housing, and a substantially cylindrical chuck plate having a rearwardly projecting threaded stem is inserted into the activating sleeve and threadably coupled thereto. The chuck plate and closer have cooperating conical surfaces therebetween, and the chuck plate is radially split so as to be elastically radially deformed inwardly for gripping a workpiece which is positionable within a recess formed in the front face of the chuck plate. The closer also mounts thereon stop pins which project axially through openings in the chuck plate into the bottom of the workpiece-receiving recess for defining a stop surface and hence a limiting or positioning plane for the workpiece.
Other objects and purposes of the invention will be apparent to persons familiar with structures of this general type upon reading the following specification and inspecting the accompanying drawings.